Leading-in wire for incandescent electric lamps



(No Model.)

. T. A. EDISON.

LEADING IN WIRE FOR INGANDESOENT ELEGTRIG LAMPS. N0. 444 53Q Patented Jan. 13, 1891.

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THOMAS A. EDISON, OF LLEWELL YX PARK, NEW' JERSEY.

LEADING-IN WIRE FOR INCANDESCENT ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent N 0. 444,530, dated January 13, 1891.

Application filed septeniher 15, 1890. Serial No. 364,946. (No model.)

To all whom it may concern.-

Be it known that I, Trrouas A. lflnisox, a citizen of the United States, residing at Llewellyn Park, county of Essex, and State of N ew Jersey, have invented a certain new and useful Improvement in Leading-in \Vires l'or Incandescent Electric Lamps, (Case No. 5375,) of which the following is a specification.

In incandescent electric lamps the incandescent filament is connected to conductors called the leading-in conductors, by means of which the filament within the sealed glass globe is connected with the circuit-wires out side of said globe. To maintain a stable vacuum it has been found best to make these leading-in wires of platinum, since its coeiiieient of expansion is so nearly that of glass that less trouble is caused by its expansion and contraction than is experienced with other metals.

The object of this invention is to economize in the amount of platinum employed and at the same time to provide a seal around the leadingin wires which shall be as nearly perfect or more. nearly perfect than with the constructions hitherto cmployed,-while at the same time an eifective support for the lilament is formed; and to this end my invention consists in the novel devices and combinations of devices hereinafter described and claimed.

In the accompanying drawings,which illustrate my improvement, Figure l is a central section of an incandescent lamp embodying my invention; Fig. 9, a section of a part of a lamp, showing a modified arrangement of the leading-in wires; and Fig. '3, a similar view showing the arrangement usually heretofore employed, for the purpose of comparison.

It is usual in the manufacture of incandescent electric lamps to introduce the platinum leading-in wires marked 1 in Fig. 3 into a glass tube, and then to fuse and compress the tube around the wires thereby tightly sealing them into the gl; .lhcse wires have necessarily been of a considerable size, not for electrical reasonsthat is, in order to be of su'lficient conducting capacity to corn vey the current without undue heatingbut for mechanical reasons, since they are re quired to support the filament and to be of such rigidity that they will not be bent by the weight of the lilament or by the jarring to which they are subject in use, transportation, tt'c. These wires are also of a considablc length, extending, as shown in Fig. 3, from the end of the filament at 2 to point 3, where they are connected with copper wires. The use of platinum wires of such size and length obviously involves avery considerable expense.

I have found that wires of copper, iron, nickel, silver, and other metals and some alloys having a greater coefficient of expansion than platinum can be sealed into the glass; but on cooling they contract sufficiently to permit air to pass into the vacuum, although they will still be held mechanically rigid by the glass. I therefore in my present invention use leading-in wires of two metals, one section being of a metal having substantially the same coeflicient of expansion as glass, such as platinum, the other being of a different and cheaper metal, and I seal both of the metals into the glass. The seal will remain perfect at the platinum sections, and itwill therefore be immaterial if the cop per or other wire contracts away from the glass, as described.

Two ways of scaling in the wires are illustrated in the drawings. In Figs. 1 and i are smaller in cross-section than the leading-in wires heretofore used. To these platinum wires are connected larger copper or other wires 5, which support and conduct the current to the filament 6. To the other end of the platinum wires are connected conductors T, which lead to the supply-circuit. The entire length of the platinum wires l, as well as a portion of the conductors 5 and 7, are sealed into the glass, as shown, these wires being laid in the glass tube and the end of the tube softened by heat and pressed down upon said wires to form a flat seal, as will be well understood. I prefer to employ platinum wire which is alloyed with iridium or other metals of the platinum group. The preferable alloy for the purpose is one containing about five per cent. of iridium. Since the size of such wire may, as stated, be made to depend solely on the electrical conditions, such wire may be made as small as will suifice to carry the current for the lamp without undue heating.

short sections ofplatinum wire several times W'hilc platinum has practically the same coefficient of expansion as certain kinds of glass, the glass used for incandescent electric lamps does not approach this quite so closely, and hence the platinum.- seal, as heretofore made with the wire of comparatively large diameter necessary for mechanical stability, has not been absolutely perfect, the contraction of the wire being greater than that of the glass; but by the use of the small wires, the proportion of the contraction being diminished and the total area available for leakage around the wires being also decreased this difliculty is avoided. Fora lamp taking one-half ampere of current, platinum wires one five-thousandths of an inch in diameter can be employed, which is evidently a very important saving. The saving in length is also of great importance. The bit of platinum wire used need only be long enough to make it practicable to attach the other section of wire to it, this being done, preferably, by fusion. A wire one-eighth of an inch in length I find to make a perfect seal. I find that copper is the preferable metal to use in practice for the terminal wires. Silver would be preferred because it does not oxidize; but on account of its low melting-point it is difficult to handle in makingthe lamp. I there.- fore prefer to use copper. This wire con.- tracts in cooling, but not sufiiciently to remove from it the mechanical support afforded is slightly dif- T he platinum wires at are of the same size as those heret-ofore used, since in this case they support the filament, but are of less length, since they extend only from the end of the filament-at 2 to the point 8 within the body of the glass, while the copper or other conductors 9 extend from that point to the outside of the lamp. Although this arrangement effects a great saving, it is not as great as in the form first described.

By comparing Figs. 1 and 2 with Fig. 3 it will be seen that in the first form theplatinum used is a very small fraction of that used in the old lamp, being both shorter and finer, while in the lamp illustrated in Fig. 2 the amount of platinum is reduced about onehalf, since the wire is reduced in length about one-half.

Having thus described my invention, what I claim is-- 1. An incandescent electric lamp having leading-in wires composed of sections of different metals, one of which sections is of a metal whose coefficient of expansion is substantially the same as that of glass, the other of a metal which has a different coefficient of expansion, and both of said sections being sealed into the glass, substantially as set forth.

2. An incandescent electric lamp having leading-in wires composed of sections of different metals, one of which sections is of a metal whose coefficient of expansion is sub stantially the same as that of glass, the other of a metal which has a different coefficient of expansion, and both of said sections being sealed into the glass, the latter section extending out of the glass, substantially as set forth.

3. An incandescent electric lamp having leading-in wires composed of a section of fine platinum wire and a section of larger wire of a different metal, the glass of the lamp .being sealed around the wire of both sections, substantially as described.

4. An incandescent electric lamp having leading-in wires of two metals, one section being a platinum wire and the rest being of a different metal, said platinum wire being sealed wholly within the glass, substantially as described.

5. An incandescent electric lamp having leading-in wires composed of three or more sections, one section being of platinum and. wholly sealed into the glass, the other section being of a difierent metal and extendingfrom the platinum-section into the sealedglobe for connection with the filament and extending in the opposite direction for connectionwith the circuit-wires. substantially as described.

This specification signed and witnessed this 12th day of September, 1890.

l l l It is hereby certified that in Letters Patent No. 444,530, granted January 13, 1891,

upon the application of Thomas A. Edison, of Llewellyn Park, New Jersey, for an improvement in Leading-in-wire for Incandescent Electric Lamps, errors appear requiring correction, as follows: In line 81, page 1, of the printed specification the Words and figures In Figs. 1 and 4 are should read In Fig. 1, 4 are, and in lines 21-22 of and that the said Letters Patent should he read with these corrections therein that the same may conform to the record of the ease in the Patent Office,

Signed, eountersigned, and sealed this 27th day of January, A. D. 1891.

CYRUS BUSSEY, Assistant Secretary of the Interior,

page 2, the word section should read sections;

[SEAL Countersigned:

O. E. MITCHELL,

'ommwissioncr of Patents.

' It is hereby certified that in Letters Patent No. 444,530, granted. January 13, 1891., upon the application of Thomas A. Edison, of Llewellyn Park, New Jersey, for an improvement in Leading-in-Wire for Incandescent Electric Lamps, errors appear reqniring correction, as follows: In line 81, page 1, of the printed Specification the Words and figures In Figs. 1 and 4 are should read In Fig. 1, 4 are, and in lines 21-22 of page 2, the word section should read sections,- and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed, conntersigned, and sealed. this 27th day of January, A. D. 1891.

[SEAL] CYRUS BUSSEY,

Assistant Secretary of the Interior.

Uountersigned:

, O. E. MITCHELL,

1 'om-missioner of Patents.

Corrections in Letters Patent No. 444,530. 

